The invention relates to an x-ray examination apparatus comprising a patient support platform, a tube stand which is movable parallel to the longitudinal axis of the horizontally positioned patient support platform, an x-ray tube which is mounted in overlying relation to the patient support platform on a tube support arm carried by the tube stand, a radiographic installation which is shiftable longitudinally of the patient support platform at an opposite side of the patient support platform from the x-ray tube, and a so-called layer rod for selective coupling engagement with the tube support arm so as to maintain alignment of the x-ray tube with the radiographic installation during a laminographic scanning operation.
In physicians' offices and smaller x-ray departments x-ray examination apparatus is frequently encountered in which the x-ray tube is mounted on a separate tube stand shiftable parallel to the longitudinal axis of the patient support platform. It is selectably usable in conjunction with a radiographic installation which is longitudinally displaceable beneath the patient support platform, such as e.g., a Bucky diaphragm or, following rotation of the tube support arm, in conjunction with an entirely different radiographic installation, such as, for example, a screen of a wall-type x-ray apparatus. For the centering of the cone of rays of the x-ray tube relative to the radiographic installation, shiftable beneath the patient support platform, it is generally conventional to provide a centering rod--also called a layer rod on account of the general utilization in the case of layer scanning (laminographic) apparatus--which, at its one end, is in engagement with the radiographic installation, and, at its other end, with the tube support arm. If, in the case of such an x-ray examination apparatus, centering relative to the radiographic installation is no longer desired, because, for example, one wishes to operate with the screen of a wall-type x-ray apparatus, an operating individual must uncouple the layer rod from the tube support arm and align the x-ray tube relative to the other radiographic installation, and vice versa.
Through the German Offenlegungsschrift 23 11 310 an x-ray examination apparatus comprising an over-table x-ray tube is known which is mounted on a tube tower drivable along the table frame. In the case of this x-ray examination apparatus, there is disposed, in the table frame, adjacent to one another, an x-ray spot film apparatus with an image intensifier television installation and a sheet film changer. Here, also, the x-ray spot film apparatus is connected by a layer rod with the tube support arm. The layer rod keeps the x-ray tube always aligned to the image layer (film) of the x-ray spot film apparatus, even in the case of oblique radiographs. If, in the case of this x-ray examination apparatus, operation is to be carried out with the sheet film changer, then the x-ray tube must be uncoupled from the layer rod and coupled with the tube tower which is always perpendicularly aligned, in order to align the path of rays perpendicularly to the patient support platform. For this purpose, an electromagnetic drive and a mechanical coupling installation are disclosed. It is a peculiar feature of this x-ray examination apparatus that, in the case of the electromagnetic as well as in the case of the mechanical design, this recoupling can be carried out only in the position of the x-ray tube in which the layer rod and the tube tower are aligned exactly parallel to one another. Also, in the case of the mechanical design, during the transition from the examination operation with the x-ray spot film apparatus to the radiography operation with the sheet film changer, the operator must always walk around the patient support platform in order to shift the clutch disk.